Electron-emitting cathode and process of preparing the same



PM Apr. 19.1927.

UNITED STATES PATENT OFFICE.

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' IoDrawlng'. Application fled January .In the manufacture of oxide-coated filaments, it is necessary that the coating adhere closelyto the filament and for this reason" there has been extensive investigation to find 6 a suitable binder to hold the oxides on the filament. The present invention relates to the use of natural guaiac which is a resinous to .the more acid rep substance belo V resentatives of the group of resins. 10

' suggested to use common-resin, but I have found that may be freed during the step o'fheating the coated filament, thereby giving. the effect of heating the'coated filament in an oxygen atmosphere. I have further found that a large reduction'in the numberof-coatings maybe efiected when a guaiac binder is used as compared with coatings in which resin. is 2 used as a binder. In addition to obtaining a filament or cathode with improved emis sion, the cost of manufacturing is reduced by lessening the number of coatings necesill manufacturing electron-emitting fila ments with a guaiac is refined y dissolving it in'methylalcohol and filtering, after'which the alcohol is evaporated. The refined 'guaiac'is then mixed with barium :and strontium hydroxides or hydrates, orcarbonates of these metals. -The mixture is then ground and distilled water is added until a thick aste is formed which is applied by successive y dip- .ping the filament in the mixture or applym'g'it with a brush. The severalcoats ar treated to reduce them to oxides. i

In the eventthat it is desirable toemploy the guaiac in solution rather than in the form of paste, carbonates of the alkali-earth metals are prepared and suspended in a diluted alcohol solution ofguaiac. The filament is thendipped'in-the solution and this operation isted' several times in order togeta pl 'ty of coatswhich are then reduced to oxides by heating.

tha event l i d f th refined moo orm. e r aiac i Wand. carbona, his areladded and I am aware that it haspreviously been guaiac absorbs oxygen which aiac' binder commercial desired to: I

14,-.1a2e. Serial m. 81,164.

stirred until the mixture solidifies. f The hot filament is then coated by taking a piece of the solid guaiac with the carbonates embedded therein and rubbing the solidified mixture on the hot filament until all porbone of. it are covered. The coating is then reduced to oxides by heating;

As illustrating oneway in which the method is carried out, one part of powdered refined guaiac. and four parts each of strontium carbonate, barium carbonate'and calcium carbonate were carefully mixed and water added so that the mixture was of such consistency that it did notdrip oil the fila ment when it was applied thereto. Ten coats of this mixture were then brushed on a platinum filament ten mils wide and onehalf mil thick by means of. a V glass-wool brush. The filament thus coated was heated in air at about 200 C. after each coat to evaporate the'water and guaiac,and thefilament was then heated in air at about 1100 C. for one-half hour to burn down the carbonates to oxides.

I claim:

1. The process of manufacturing an elec tron-emitting cathode which consists in coating an electrical conductor with a compound of the alkali-earth group mixed with a material which absorbs oxygen, and then heat ing the coated conductor.

. 2. The process of manufacturing an electron-emitting cathode which consists in coating an electrical conductor with a compound of the alkali-earth group mixed with guaiac.

3.' The process of manufacturing an elec: 85 tron-emitting cathode which consists'in coating an electrical conductor with a compound of the alkali-earth group" held in a guaiac binder, and then su jectin'g the-coated filament to heat. r 4. The recess of manufacturing an electron-emittmg cathode which consists in coating an electrical conductor with a mixture comprising a compound of the alkali-earth up and a guaiac paste, and then sub-. ecting the coated filament to heat.

whereof I aflix my'signature. BEDERICK IIOLBOBN.

In testimon. 

